1. Field of the Invention
The present invention relates to a process for manufacturing a semiconductor device involving dry etching an organic resist layer on a substrate on which another layer is subsequently formed.
2. Description of the Related Art
The processing of a semiconductor substrate using a resist layer of an organic material including a photoresist as a mask is widely used in the manufacture of semiconductor devices. In this processing, a resist layer is locally formed on a part of a semiconductor substrate, for example, an eptaxial layer, and subsequently, selective etching, ion implantation, etc., are carried out on the semiconductor substrate using the resist layer as a mask. The resist layer is then removed. To remove the resist layer, wet etching, for example, chemical etching, has been used, but dry etching such as plasma etching is now increasingly used since the disposal of waste matters is easier in dry etching than in wet etching. Therefore, there is a desire to use dry etching in the removal of a resist layer used as a mask in the processing of a semiconductor substrate.
However, although a resist layer of an organic material can be removed by wet etching without problems, the removal of a resist layer of an organic material on a substrate by dry etching causes the formation of particles on the surface of the substrate, and as a result, a layer deposited thereon becomes rough surface. For example, if a polycrystalline silicon layer is deposited on a substrate containing the particles as mentioned above, bright points (particles which can be observed as bright point in the dark field of microscope) appear in the polycrystalline silicon layer, which are nuclei of crystal defects, and the thickness of the resulting polycrystalline silicon layer is non-uniform or the top surface of the polycrystalline silicon layer is uneven. These defects, rough surface, etc., may cause a deterioration of the characteristics of semiconductor devices having such a polycrystalline silicon layer or of another layer superimposed on the polycrystalline polysilicon layer, which may have reflected defects or rough surface.
Accordingly, it has been considered that dry etching should not be used for the removal of a resist layer, and the reasons therefor have not been investigated.